Connecting transparent optical components to metal attachment elements is known per se. Depending upon the application, the connections can be produced by clamping, gluing or in other ways.
Highly sensitive optics are used, for example, in semiconductor manufacture for exposing wafers. To expose photomasks with ultraviolet light, an extremely high precision of attachment is required for highly sensitive optics. A simple clamping of an optical component between metal parts is therefore generally viewed as inadequate. The use of adhesives for attaching the optical component to a metal fixture is often unwanted because adhesives of this kind emit gas and the gas-emitting components are absorbent in the ultraviolet range required for making exposures.
German patent publication 4,216,337 discloses a component for an optic, optoelectronic or electronic apparatus which has parts made of two metals which are to be connected to each other and which exhibit different thermal coefficients of expansion. A connecting part, which is manufactured by roll-bonded cladding, is inserted between the parts made of different metals. The connection of the connecting part to the parts, which are to be connected to each other, is made by welding, soldering or gluing.
European patent publication 0,106,230 discloses a method for mounting and adjusting cavity mirrors of a laser. In this publication, mirror supports are connected by wringing to a base made of the same material.
It is also known to join metals to non-metals by ultrasonic welding. A method of ultrasonic welding for this purpose is disclosed in German Patent 2,312,724. Here, a method and an apparatus are disclosed for welding a metal part to a non-metal part having a precious metal coating such as a piezoceramic platelet but also a quartz or glass disc with the insertion of a further intermediate layer comprising a metal. In the method, an aluminum layer or foil is applied to the mutually adjacent connecting surfaces of the metal part and of the non-metal part, then the non-metal part is fixed and the aluminum coated connecting surfaces are placed one atop the other and preheated to a temperature of at least 250.degree. C. and preferably 350.degree. C. Finally, these preheated parts are connected to each other by ultrasonic welding. It is noted as being especially advantageous to preheat the metal parts in a high frequency electromagnetic field. With this additional external heating (especially of an aluminum layer), it is intended to obtain a homogeneous total surface weld connection and to greatly decrease the sonic energy. This sonic energy is applied to ultrasonically weld the component and often leads to the destruction of the non-metal component.
It is suggested to provide the aluminum intermediate layer by vaporization, sputtering in a plasma light arc or to provide the aluminum intermediate layer in the form of an aluminum foil which is inserted between the components to be connected by welding. It is problematic that the parts have to be preheated to high temperatures and that a total-area connection is intended to be achieved. The total-area connection to the metal carrier hinders the application with transmissive optics.
In German Patent 195 46 997, it is mentioned that, to connect parts of aluminum to parts of ceramic, first the intended connecting region of the ceramic part can be metallized by burning in a metal paste, thermal sputtering or the like so that thereafter, the actual connection can be made by hard soldering. As an alternative, it is suggested in this patent to make the connection by friction welding with a specific form of movement.
A series of scientific papers is directed to the ultrasonic welding of metal and glass. Exemplary here is the article of E. Roeder et al entitled "Neue Werkstoffverbunde durch Ultraschallschwei.beta.en" published in "Technologie & Management", volume 44 (1995) starting at page 31. Another article directed to this subject matter is that of U. Schlicker et al entitled "Ultraschall-Rollnahtschwei.beta.en von Glas und Keramik mit Metall" published in "Schwei.beta.en & Schneiden", volume 49, (1997), starting at page 564.
In the last-mentioned article, the suggestion is made that a sonotrode is pressed via a static welding force to the parts to be joined and rolls onto the joining parts which are moved along synchronously therewith. In this process, the energy needed for joining is applied in the same manner as for the ultrasonic welding of metals in the form of mechanical shearing waves into the joining part facing toward the sonotrode. The coupling takes place because of the higher mechanical load at the sonotrode side and the more favorable coupling of the ultrasonic vibration via the metal workpiece; whereas, the non-metal joining part is placed on a rubber support so as to be fixed against slippage in order to ensure a relative movement to the metal welding partner vibrating transversely to the welding direction. It is suggested to reduce the joining temperature with a coolant and thereby obtain a reduction of the inherent stress in the joint.